The present application claims priority under 35 U.S.C. xc2xa7119 to Japanese Patent Application No. 2001-272361, filed Sep. 7, 2001, the entire contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a drive shaft support structure for a small watercraft. More particularly, the present invention relates to a drive shaft support structure for a small watercraft in which an impeller is driven by a drive shaft connected to an output shaft of an engine mounted in a boat body.
2. Description of Background Art
A conventional drive shaft support structure for a small watercraft is shown in FIG. 7.
FIG. 7 shows an engine 1 mounted on a boat body 2, and a drive shaft (hereinafter referred also to simply as a shaft) 4 connected to an output shaft 1a of the engine 1 through a coupler 3. An impeller 5a of a jet pump 5 is fixed to the rear end of a shaft 4. When the impeller 5a is rotationally driven by the engine 1 through the shaft 4, water is taken in through a water intake port 2a provided at the bottom of the boat and is jetted from a nozzle 5b, whereby the boat is propelled forward.
The boat body 2 is provided with a cylindrical portion 2b through which the shaft 4 passes and which extends from the outside of the boat toward the engine 1, and a support portion 2c for supporting a rubber dampered bearing body 6 rotatably supporting the shaft 4 on the engine 1 side.
The bearing body 6 includes a metallic cylindrical member 6a, a bearing member 6b mounted in the cylindrical member 6a, a rubber damper portion 6c formed integrally with the outer circumference of the bearing body 6, and a reinforcement member 6d integral with the rubber damper portion 6c. The bearing body 6 is fixed to the support portion 2c by passing a bolt 6e through the reinforcement member 6d, mating a nut 6f to the bolt 6e, and fastening the nut 6f. 
A tubular body 7 is disposed in an intermediate position between the bearing body 6 and the support portion 2c. The tubular body 7 includes a tubular portion 7a extending toward the tubular portion 2b of the boat body 2 and a flange portion 7b. The tubular body 7 is fixed to the support portion 2c by fastening the flange portion 7b to the bearing body 6 with a bolt 6e and nut 6f. 
The rear end of the tubular body 7 and a tip end portion of the tubular portion 2b of the boat body 2 are connected to each other by a rubber sleeve 8. In this condition, both ends of the rubber sleeve 8 are fastened by ring-shaped clamps 9, 9.
According to this conventional shaft support structure, the shaft 4 can be rotatably supported by the rubber dampered bearing body 6 to absorb some of the oscillation of the shaft 4.
While some penetration of water W inside the boat body 2 can be prevented through the tubular portion 2b of the boat body 2 can be prevented to a certain degree by the rubber sleeve 8, the tubular body 7, and the rubber dampered bearing body 6, it is difficult to ensure. More specifically, with this conventional structure, water W tends to penetrate into the boat body 2 through the tubular portion 2b at one or more of the following points:
the connection portion C1 between the tubular portion 2b and a rear end portion of the rubber sleeve 8;
the connection portion C2 between a tip end portion of the rubber sleeve 8 and a tip end portion of the tubular body 7;
the joint portion C3 between the flange portion 7b of the tubular body 7 and the bearing body 6; and
the joint portion C4 between the flange portion 7b of the tubular body 7 and the support portion 2c. 
In summary, it has been difficult to ensure that water will not penetrate the boat body 2. Even if the flange portion 7b of the tubular body 7 and the support portion 2c are tightly joined to each other with an adhesive, water is still likely to penetrate at least the three portions C1 to C3.
It is an object of the present invention is to provide a drive shaft structure for small watercraft which solves the at least the above problem of water seeping into the boat body through a tubular portion of the boat body.
In order to attain the above object, the present invention provides a drive shaft support structure for small watercraft, which includes an impeller in which the drive shaft is connected to an output shaft of an engine mounted in a boat body. The boat body is provided with a cylindrical portion extending from the outside of the boat body toward the engine, through which the drive shaft passes. Also provided is a rubber dampered bearing body which rotatably supports the drive shaft on the engine side so that it does not contact the cylindrical portion. The rubber dampered bearing body is supported by a support portion, and includes a rubber damper portion and a rubber cylindrical portion which extends toward the cylindrical portion, the rubber cylindrical portion being formed integrally with the rubber damper portion. The rubber cylindrical portion and the cylindrical portion are connected directly to each other.
The rubber cylindrical portion is provided with a grease supply hole for supplying grease to a water seal portion of the rubber dampered bearing body, and a grease supply hose is connected to the grease supply hole.
An engine output shaft and the drive shaft are connected to each other through a coupler having a coupler cover, the rear end of the coupler cover being supported by the rubber damper bearing body.
The drive shaft support structure for small watercraft includes the impeller driven through the drive shaft connected to the output shaft of the engine mounted in the boat body, wherein the boat body is provided with the cylindrical portion through which a drive shaft is passed and which extends from the outside of the boat toward the engine. A support portion for supporting the rubber dampered bearing body rotatably supporting the drive shaft on the engine side from the cylindrical portion is also provided. The rubber dampered bearing body includes a rubber cylindrical portion formed integrally with the rubber damper portion of the rubber dampered bearing body, and the rubber cylindrical portion and the cylindrical portion are connected directly to each other.
As a result, water which may otherwise penetrate a conventional boat body is prevented from entering the boat interior by the present invention. This is due to the fact that the present invention includes only one point where water may possibly enter, namely, the connection portion between the rubber cylindrical portion and the cylindrical portion on the boat body side. Thus, it is more difficult for water to penetrate into the boat through the cylindrical portion of the boat body than with conventional structures.
Moreover, the rubber cylindrical portion is formed integrally with the rubber damper portion of the rubber dampered bearing body, and the rubber cylindrical portion and the cylindrical portion are connected directly to each other. As a result of this structure, the number of component parts is markedly reduced as compared with the prior art. The tubular body 7, the rubber sleeve 8, and one of the two clamps 9, 9 of the conventional boats become unnecessary, and thus the assembly tasks are reduced.
With the present invention, the rubber cylindrical portion is provided with the grease supply hole for supplying grease to the water seal portion of the rubber dampered bearing body, and the grease supply hose is connected to the grease supply hole. As a result, grease can be easily supplied to the water seal portion of the bearing body through the grease supply hose. This feature acts to prevent water from entering into the inside of the boat body through the cylindrical portion of the boat body.
Further as described above, the output shaft of the engine and the drive shaft are connected to each other through the coupler, and the coupler is provided with the coupler cover for covering the coupler. Without a cover, if water were to penetrate into the boat body it would be scattered by making contact with the coupler. This would occur if water were to penetrated the body through other portions than the connection portion between the rubber cylindrical portion and the cylindrical portion on the boat body side.
With the present invention, however, the scattering of water is prevented, since the coupler is covered by the coupler cover. In addition, since the rear end of the coupler cover is supported by the rubber dampered bearing body, a vibration-damping effect by the rubber damper is obtained.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.